xref: /kernel/linux/linux-5.10/net/netrom/nr_out.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5 * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
6 */
7#include <linux/errno.h>
8#include <linux/types.h>
9#include <linux/socket.h>
10#include <linux/in.h>
11#include <linux/kernel.h>
12#include <linux/timer.h>
13#include <linux/string.h>
14#include <linux/sockios.h>
15#include <linux/net.h>
16#include <linux/slab.h>
17#include <net/ax25.h>
18#include <linux/inet.h>
19#include <linux/netdevice.h>
20#include <linux/skbuff.h>
21#include <net/sock.h>
22#include <linux/uaccess.h>
23#include <linux/fcntl.h>
24#include <linux/mm.h>
25#include <linux/interrupt.h>
26#include <net/netrom.h>
27
28/*
29 *	This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
30 *	cannot be fragmented in this manner.
31 */
32void nr_output(struct sock *sk, struct sk_buff *skb)
33{
34	struct sk_buff *skbn;
35	unsigned char transport[NR_TRANSPORT_LEN];
36	int err, frontlen, len;
37
38	if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
39		/* Save a copy of the Transport Header */
40		skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
41		skb_pull(skb, NR_TRANSPORT_LEN);
42
43		frontlen = skb_headroom(skb);
44
45		while (skb->len > 0) {
46			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
47				return;
48
49			skb_reserve(skbn, frontlen);
50
51			len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
52
53			/* Copy the user data */
54			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
55			skb_pull(skb, len);
56
57			/* Duplicate the Transport Header */
58			skb_push(skbn, NR_TRANSPORT_LEN);
59			skb_copy_to_linear_data(skbn, transport,
60						NR_TRANSPORT_LEN);
61			if (skb->len > 0)
62				skbn->data[4] |= NR_MORE_FLAG;
63
64			skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
65		}
66
67		kfree_skb(skb);
68	} else {
69		skb_queue_tail(&sk->sk_write_queue, skb);		/* Throw it on the queue */
70	}
71
72	nr_kick(sk);
73}
74
75/*
76 *	This procedure is passed a buffer descriptor for an iframe. It builds
77 *	the rest of the control part of the frame and then writes it out.
78 */
79static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
80{
81	struct nr_sock *nr = nr_sk(sk);
82
83	if (skb == NULL)
84		return;
85
86	skb->data[2] = nr->vs;
87	skb->data[3] = nr->vr;
88
89	if (nr->condition & NR_COND_OWN_RX_BUSY)
90		skb->data[4] |= NR_CHOKE_FLAG;
91
92	nr_start_idletimer(sk);
93
94	nr_transmit_buffer(sk, skb);
95}
96
97void nr_send_nak_frame(struct sock *sk)
98{
99	struct sk_buff *skb, *skbn;
100	struct nr_sock *nr = nr_sk(sk);
101
102	if ((skb = skb_peek(&nr->ack_queue)) == NULL)
103		return;
104
105	if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
106		return;
107
108	skbn->data[2] = nr->va;
109	skbn->data[3] = nr->vr;
110
111	if (nr->condition & NR_COND_OWN_RX_BUSY)
112		skbn->data[4] |= NR_CHOKE_FLAG;
113
114	nr_transmit_buffer(sk, skbn);
115
116	nr->condition &= ~NR_COND_ACK_PENDING;
117	nr->vl         = nr->vr;
118
119	nr_stop_t1timer(sk);
120}
121
122void nr_kick(struct sock *sk)
123{
124	struct nr_sock *nr = nr_sk(sk);
125	struct sk_buff *skb, *skbn;
126	unsigned short start, end;
127
128	if (nr->state != NR_STATE_3)
129		return;
130
131	if (nr->condition & NR_COND_PEER_RX_BUSY)
132		return;
133
134	if (!skb_peek(&sk->sk_write_queue))
135		return;
136
137	start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs;
138	end   = (nr->va + nr->window) % NR_MODULUS;
139
140	if (start == end)
141		return;
142
143	nr->vs = start;
144
145	/*
146	 * Transmit data until either we're out of data to send or
147	 * the window is full.
148	 */
149
150	/*
151	 * Dequeue the frame and copy it.
152	 */
153	skb = skb_dequeue(&sk->sk_write_queue);
154
155	do {
156		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
157			skb_queue_head(&sk->sk_write_queue, skb);
158			break;
159		}
160
161		skb_set_owner_w(skbn, sk);
162
163		/*
164		 * Transmit the frame copy.
165		 */
166		nr_send_iframe(sk, skbn);
167
168		nr->vs = (nr->vs + 1) % NR_MODULUS;
169
170		/*
171		 * Requeue the original data frame.
172		 */
173		skb_queue_tail(&nr->ack_queue, skb);
174
175	} while (nr->vs != end &&
176		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
177
178	nr->vl         = nr->vr;
179	nr->condition &= ~NR_COND_ACK_PENDING;
180
181	if (!nr_t1timer_running(sk))
182		nr_start_t1timer(sk);
183}
184
185void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
186{
187	struct nr_sock *nr = nr_sk(sk);
188	unsigned char *dptr;
189
190	/*
191	 *	Add the protocol byte and network header.
192	 */
193	dptr = skb_push(skb, NR_NETWORK_LEN);
194
195	memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
196	dptr[6] &= ~AX25_CBIT;
197	dptr[6] &= ~AX25_EBIT;
198	dptr[6] |= AX25_SSSID_SPARE;
199	dptr += AX25_ADDR_LEN;
200
201	memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
202	dptr[6] &= ~AX25_CBIT;
203	dptr[6] |= AX25_EBIT;
204	dptr[6] |= AX25_SSSID_SPARE;
205	dptr += AX25_ADDR_LEN;
206
207	*dptr++ = sysctl_netrom_network_ttl_initialiser;
208
209	if (!nr_route_frame(skb, NULL)) {
210		kfree_skb(skb);
211		nr_disconnect(sk, ENETUNREACH);
212	}
213}
214
215/*
216 * The following routines are taken from page 170 of the 7th ARRL Computer
217 * Networking Conference paper, as is the whole state machine.
218 */
219
220void nr_establish_data_link(struct sock *sk)
221{
222	struct nr_sock *nr = nr_sk(sk);
223
224	nr->condition = 0x00;
225	nr->n2count   = 0;
226
227	nr_write_internal(sk, NR_CONNREQ);
228
229	nr_stop_t2timer(sk);
230	nr_stop_t4timer(sk);
231	nr_stop_idletimer(sk);
232	nr_start_t1timer(sk);
233}
234
235/*
236 * Never send a NAK when we are CHOKEd.
237 */
238void nr_enquiry_response(struct sock *sk)
239{
240	struct nr_sock *nr = nr_sk(sk);
241	int frametype = NR_INFOACK;
242
243	if (nr->condition & NR_COND_OWN_RX_BUSY) {
244		frametype |= NR_CHOKE_FLAG;
245	} else {
246		if (skb_peek(&nr->reseq_queue) != NULL)
247			frametype |= NR_NAK_FLAG;
248	}
249
250	nr_write_internal(sk, frametype);
251
252	nr->vl         = nr->vr;
253	nr->condition &= ~NR_COND_ACK_PENDING;
254}
255
256void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
257{
258	struct nr_sock *nrom = nr_sk(sk);
259
260	if (nrom->vs == nr) {
261		nr_frames_acked(sk, nr);
262		nr_stop_t1timer(sk);
263		nrom->n2count = 0;
264	} else {
265		if (nrom->va != nr) {
266			nr_frames_acked(sk, nr);
267			nr_start_t1timer(sk);
268		}
269	}
270}
271